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Species Page

Tremex wasp

Tremex fuscicornis

Distribution

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Host plants / species affected

Main hosts

show all species affected
Acer negundo (box elder)
Acer platanoides (Norway maple)
Alnus (alders)
Alnus japonica (Japanese alder)
Betula (birches)
Betula pubescens (Downy birch)
Carpinus betulus (hornbeam)
Celtis sinensis (Chinese elm)
Fagus (beeches)
Fagus sylvatica (common beech)
Juglans regia (walnut)
Populus alba (silver-leaf poplar)
Populus deltoides (poplar)
Populus nigra (black poplar)
Populus nigra var. italica
Populus sp. (poplar)
Populus tremula (aspen (European))
Prunus (stone fruit)
Prunus yedoensis
Pterocarya stenoptera (chinese wing nut)
Quercus (oaks)
Robinia pseudoacacia (black locust)
Salix (willows)
Salix babylonica (weeping willow)
Salix humboldtiana
Ulmus (elms)
Ulmus davidiana (japanese elm)
Zelkova
Zelkova serrata (Japanese selkova)

List of symptoms / signs

Leaves - wilting
Leaves - yellowed or dead
Stems - internal feeding
Stems - visible frass
Whole plant - plant dead; dieback

Symptoms

The symptoms of attack by T. fuscicornis in dead and dying trees are limited to the presence of round adult emergence holes, approximately 5 to 6 mm in diameter, in trees where this insect has completed its life cycle. Attacked trees develop thin or chlorotic foliage and ultimately die.

Prevention and control

At present, direct control methods are not available for this insect. The following measures are suggested in cases where the introduction and establishment of T. fuscicornis results in the death of healthy trees. These are based on pest management measures currently in place for Sirex noctilio, in areas where this insect has been introduced in Southern Hemisphere pine plantations.
Cultural Control

Forests, shelter-belts and ornamentals can be kept in a vigorous condition through regular scheduled thinning and proper watering. Other cultural measures include the rapid removal of freshly-cut logs of broadleaf species from forested areas during timber harvesting operations. The storage of logs under water sprays, debarking or rapid processing should be used to prevent wood wasp attacks in sawmills.

Chemical Control

Chemical control measures have not been developed for wood wasps of the family Siricidae.

Mechanical Control

The fumigation and exposure of lumber and other wood products to high temperatures would kill all life stages of this insect.

Biological Control

If T. fuscicornis is introduced and established in conifer forests outside its geographic range and causes losses, the introduction of insect parasitoids in a classical biological control programme would be a potentially viable tactic.

Pheromonal Control

Siricids tend to respond to host attractants and are not known to produce attractant pheromones. Consequently, pheromonal control is not a viable pest management tactic.

Field Monitoring

A trap-tree technique, used to monitor for the presence of Sirex noctilio, should also be effective for T. fuscicornis. This involves the injection of an herbicide into suppressed trees, which stresses them and makes them attractive to attack.

Integrated Pest Management

In Chile, an integrated approach that uses a combination of cutting and destroying infested trees plus the introduction of natural enemies, is under development. Low-level populations can be detected by establishing trap-trees, which are injected with a weak herbicide to make them attractive to adult T. fuscicornis. The parasitoid, Ibalia leucospoides is being evaluated as a potential biological control agent. The use of a parasitic nematode, which is an effective control for the wood wasp, Sirex noctilio, is also being considered (Baldini, 2002).

Impact

In their native habitats, the larvae of wood wasps bore into weakened and dying trees. They are usually considered to be of minor importance except for decreasing the value of lumber (Smith and Schiff, 2002). In its natural range, populations of T. fuscicornis are typically small and difficult to observe (Baldini, 2002). However, a report from the Ukraine indicated that outbreaks of this insect have occurred in birch and other broadleaf species (Kolomets, 1998).

In Chile, weakened, damaged or recently-cut trees are preferred. However, apparently vigorous trees of some hosts, such as Acer negundo, may also suffer attack. On vigorous trees, the first attacks occur on the branches. These cause dieback and weakening of the trees. The brood adults that emerge from the branches subsequently infest the main bole. All trees that are attacked are killed (Baldini, 2002). To date, extensive damage has occurred to windbreak and shelter-belt plantings (Baldini, 2002). The attacks are typically so heavy that a single poplar can produce 2000 individual brood adults (Baldini, 2002). Therefore, the wood is impossible to use for lumber or other wood products. Moreover, the rate of decay of infested wood is accelerated because of the action of the symbiotic fungi associated with T. fuscicornis (Baldini, 2002). Another significant impact has been the loss of poplar windbreak plantings around agricultural crops and fruit orchards. This exposes the orchards to high winds and results in reduced crop yields (Baldini, 2002).